Robotics in Nuclear Disaster Response

Kevin Mori
March 25, 2013

We live in a day and age in which robots build our
automobiles, delicately perform surgery deep within the body, and repair
oil leaks nearly a mile below the sea surface. One would expect robots
to play a linchpin role in the response to the Fukushima Nuclear Power
Plant accident of March 2011. Yet just months on the scene, Quince,
Japan's $6 million robot, became trapped in the confined spaces of the
power plant. [1] Two years after the accident, it is still a hostage to
Fukushima.

Notably, at least three robots have been sent to
Fukushima from iRobot, a U.S. company most famous for its household
robotic vacuum cleaners. We have a special glimpse into the front line
rescue operations of these robots through the blog of "S.H.," a
Fukushima robot operator who candidly documents his daily work.
Although once publicly available, the blog has since been shut down for
reasons not made public. Fortunately, an IEEE Spectrum writer has
archived the website and published excerpts of it on the publication's
website. [2]

Challenges of Robotic Nuclear Response

Why is repair work in a nuclear plant a few hundred
meters away so much more challenging than stopping an oil leak at the
sea floor, a thousand meters from the surface? For one, the plant is
strewn with rubble, making access difficult even for rescuers. Although
robots can be sent into these dangerous areas without risking human
lives, a stuck robot like Quince is more than just costly - it can
impair access for other robots in tight spaces like stairwells or
doorways. It may be tempting to relegate details like stairwell access
to the realm of practicalities that can be overcome by a skilled
operator, but in fact, many of these details can easily grow to become
major sources of delay or complete showstoppers. S.H. writes with pride
of how he was the first to successfully open a round door knob with a
robot. When iRobot sent the Warrior, a larger robot, S.H. pointed out
the difficulty of navigating narrow stairwells and humorously
photographs holes the robot punched in the drywall as he was practicing.
[2]

Beyond the difficulties of dexterous locomotion and
manipulation, nuclear response robots face the twin challenge of intense
radiation exposure and unreliable wireless communications. Radiation
can damage electronics in two ways: by physical damage to the
semiconductor crystal structure by near field neutrons and by shifting
electrical charges due to ionizing gamma and X-ray radiation. [3] In
either case, the operating characteristics of individual electronic
components shift, resulting in device failure. So-called
radiation-hardened devices are tested by measuring the total dosage
(often in Sieverts) they can withstand before malfunction. But since
radioactive damage is statistical, device survival is never guaranteed.
S.H. notes in his blog that the video image from the robots became
distorted as he piloted the robot near radioactive hot spots. [2]

Of course, reactor electronics must be designed to be
radiation-resistant as well. This is accomplished by a combination of
radiation-hardening and shielding. The latter approach causes
communication challenges for rescuers as the heavy concrete and lead
structures of a reactor limit wireless reliability. S.H. describes a
repeater strategy the team improvised to extend the communication range
of a robot: a helper robot is stationed part way in the plant, tethered
to a fiber optic cable so that the first robot has extended radio range
deep within the plant.

As one would predict, the challenges are not strictly
technical either. S.H. documents frustrations with the sometimes
erratic planning by his superiors and personality conflicts between the
front line workers and the distanced management. He even recounts a day
where an employee from a different branch of Tokyo Electric Power drives
a truck over a robot's communication cable, risking a severed cable and
a second stranded robot. Traffic cones clearly marked the cable and
S.H. told the truck driver he could not drive over it, but he was
deliberately ignored. Such incidents are an inevitable part of complex
disaster response highlighting the importance of effective management
and respect between all groups involved.

Designing for Disaster

All of these struggles raise a larger question over
the design of nuclear reactors. Artificial intelligence pioneer Marvin
Minsky writes, "I am appalled by the nuclear industry's inability to
deal with the unexpected...The big problem today is that nuclear plants
are not designed for telepresence." [4] In contrast to a nuclear power
plant, many of the valves and actuators on deep sea equipment have been
specially designed for easy use by robotic manipulators. Automobile
manufacturing plants are now designed with robotic integration as a top
priority and medical devices are now specially designed for robotic
platforms. Little has changed in the robot-readiness of nuclear power
plants since Three Mile Island thirty years ago, when three robots were
designed by Carnegie Mellon University for survey and decontamination of
the unit 2 reactor. [5] Interestingly, the third robot, dubbed
Workhorse, was intended to help decontaminate and disassemble highly
radioactive structures inside the plant, but it was never deployed due
to cost and complexity concerns.

What explains the lack of progress? No certain
answers exist, for this is a topic deeply intertwined with public
perception and politics. Eiji Koyanagi, vice director of the Future
Robotics Technology Center in Japan hypothesizes that funding for
Japanese nuclear response robotics dried up after the 1999 Tokaimura
accident, because the country was trying to protect the impression it
had painstakingly created of the near-absolute safety of nuclear power.
Koyanagi says funding such research would have meant that, "people were
obviously going to ask, 'Wait, is there going to be a situation so
dangerous that humans can't enter the plant?'". [1] It remains to be
seen if this attitude will shift after Fukushima as Japan struggles to
rebuild its confidence in a vital source of its energy.